1  # coding: utf-8
   2  # frozen_string_literal: true
   3 
   4 
   5 
   6  module Umu
   7 
   8  module AbstractSyntax
   9 
  10  module Core
  11 
  12  module Expression
  13 
  14  module Nary     # N-ary, where N >= 3
  15 
  16  class Let < Expression::Abstract
  17      attr_reader :decls, :expr
  18 
  19 
  20      def initialize(loc, decls, expr)
  21          ASSERT.kind_of decls,   ASCD::SeqOfDeclaration
  22          ASSERT.kind_of expr,    ASCE::Abstract
  23 
  24          super(loc)
  25 
  26          @decls  = decls
  27          @expr   = expr
  28      end
  29 
  30 
  31      def to_s
  32          format(
  33              "%%LET { %s %%IN %s }",
  34              self.decls.map(&:to_s).join(' '),
  35              self.expr
  36          )
  37      end
  38 
  39 
  40      def pretty_print(q)
  41          PRT.group_for_enum q, self.decls, bb:'%LET {', sep:' '
  42 
  43          q.breakable
  44 
  45          PRT.group q, bb:'%IN', eb:'}', sep:' ' do
  46              q.pp self.expr
  47          end
  48      end
  49 
  50 
  51  private
  52 
  53      def __evaluate__(init_env, event)
  54          ASSERT.kind_of init_env,    E::Entry
  55          ASSERT.kind_of event,       E::Tracer::Event
  56 
  57          new_env = self.decls.inject(init_env.enter(event)) { |env, decl|
  58              ASSERT.kind_of env,     E::Entry
  59              ASSERT.kind_of decl,    ASCD::Abstract
  60 
  61              result = decl.evaluate env
  62              ASSERT.kind_of result, ASR::Environment
  63 
  64              result.env
  65          }
  66 
  67          final_result = self.expr.evaluate new_env
  68          ASSERT.kind_of final_result, ASR::Value
  69 
  70          final_result.value
  71      end
  72  end
  73 
  74  end # Umu::AbstractSyntax::Core::Expression::Nary
  75 
  76 
  77  module_function
  78 
  79      def make_let(loc, decls, expr)
  80          ASSERT.kind_of loc,     LOC::Entry
  81          ASSERT.kind_of decls,   ASCD::SeqOfDeclaration
  82          ASSERT.kind_of expr,    ASCE::Abstract
  83 
  84          Nary::Let.new(loc, decls.freeze, expr).freeze
  85      end
  86 
  87  end # Umu::AbstractSyntax::Core::Expression
  88 
  89  end # Umu::AbstractSyntax::Core
  90 
  91  end # Umu::AbstractSyntax
  92 
  93  end # Umu